Decadal biodiversity trends in rivers reveal recent community rearrangements.

While it is recognized that biodiversity currently declines at a global scale, we still have an incomplete understanding of local biodiversity trends under global change. To address this deficiency, we examined the recent decadal trends in water quality and biodiversity (taxonomic and functional) of key river organisms (diatoms, macroinvertebrates and fish) in France. We implemented regression, RLQ and fourth-corner analyses. Our results showed that nutrient loads tended to decrease, diatom richness tended to decline and macoinvertebrate richness tended to increase. The recovery of sensitive taxa in all three groups suggested a successful outcome of water quality management in France over the past decades. Our study further revealed consistent rearrangements within river communities, with a decrease in the ratio of planktonic to benthic diatoms, and corresponding functional changes in macroinvertebrate and fish trait composition, indicative of a trophic cascade in response to changes in environmental conditions.

Polar organic chemical integrative samplers as an effective tool for chemical monitoring of surface waters - Results from one-year monitoring in France.

In an effort to support European Union Water Framework Directive goals, we have set up a national demonstrator project to identify the advantages and limitations of passive samplers for regulatory monitoring of polar contaminants in surface waters. Here we carried out successive 14 day-deployments of polar organic chemical integrative samplers (POCIS) for one year at three sites. In parallel, we used the passive sampler deployment/retrieval operations to collect spot water samples for comparative analysis. We observed that frequency of quantification was significantly higher in POCIS than spot samples for 29 contaminants, similar for 15, and lower for one, because POCIS lowered the limits of quantification for most contaminants (median value factor of 11). We built a database of sampling rates (Rs) according to quality indices to convert concentrations in POCIS to concentrations in water (23 contaminants with a high-quality median Rs value, 20 with an approximate Rs and two with no usable Rs). Several phenomena were observed over one-year monitoring period. For example, after a flood episode, dilution phenomenon in rivers is correctly observed by using POCIS sampling whereas significant concentration increased due to soil leaching is observed with both passive and spot sampling. Cases of episodic contamination that were missed by spot sampling were observed with POCIS as it was able to capture contamination of short duration but sufficient intensity. Contamination by pharmaceuticals was found to come from wastewater treatment plant discharges and showed relatively little variation over the course of the year in both POCIS and spot samples. POCIS enables more reliable annual monitoring of pesticide and pharmaceutical contamination than spot sampling. Furthermore, POCIS also improves the environmental quality standards based assessment of chemical status and on annual average concentrations compared to spot sampling. This study demonstrates the value and practicability of POCIS-based chemical monitoring for use in regulatory control networks.

Comparability of ecological quality boundaries in the Mediterranean basin using freshwater benthic invertebrates. Statistical options and implications.

Within the Mediterranean region each country has its own assessment method based on aquatic macroinvertebrates. However, independently of the classification system, quality assessments should be comparable across members of the European Commission, which means, among others, that the boundaries between classes should not deviate significantly. Here we check for comparability between High-Good and Good-Moderate classifications, through the use of a common metric. Additionally, we discuss the influence of the conceptual and statistical approaches used to calculate a common boundary within the Mediterranean countries participating in the Intercalibration Exercise (e.g., using individual national type-boundaries, one value for each common type or an average boundary by country; weighted average, median) in the overall outcome. All methods, except for the IBMWP (the Iberian BMWP) when applied to temporary rivers, were highly correlated (0.82

Least Disturbed Condition for European Mediterranean rivers.

The present report describes a three-step approach that was used to characterize and define thresholds for the Least Disturbed Condition in Mediterranean streams of four different types, regarding organic pollution and nutrients, hydrological and morphological alterations, and land use. For this purpose, a common database composed of national reference sites (929 records) from seven countries, sampled for invertebrates, diatoms and macrophytes was used. The analyses of reference sites showed that small (catchment <100 km(2)) siliceous and non-siliceous streams were mainly affected by channelization, bank alteration and hydropeaking. Medium-sized siliceous rivers were the most affected by stressors: 25-43% of the samples showed at least slight alterations regarding channelization, connectivity, upstream dam influence, hydropeaking and degradation of riparian vegetation. Temporary streams were the least affected by hydromorphological changes, but they were nevertheless affected by alterations in riparian vegetation. There were no major differences between all permanent stream types regarding water quality, but temporary streams showed lower values for oxygenation (DO) and wider ranges for other variables, such as nitrates. A lower threshold value for DO (60%) was determined for this stream type and can be attributed to the streams' natural characteristics. For all other river types, common limits were found for the remaining variables (ammonium, nitrate, phosphate, total P, % of artificial areas, % of intensive and extensive agriculture, % of semi-natural areas in the catchment). These values were then used to select the list of reference sites. The biological communities were characterized, revealing the existence of nine groups of Mediterranean invertebrate communities, six for diatoms and five for macrophytes: each group was characterized by specific indicator taxa that highlighted the differences between groups.

Occurrence and persistence of bacterial and viral faecal indicators in wastewater biofilms.

Biofilms within wastewater treatment plants can capture enteric microorganisms initially present in the water phase immobilising them either definitively or temporarily. Consequently, fates of microorganisms may totally change depending on whether they interact or not with biofilms. In this study, we assessed the stability of wastewater biofilms comparing the evolution of the concentrations of bacteria (heterotrophic plate count [HPC], thermotolerant coliforms [TC]) and viral (somatic coliphages [SC] and F-specific phages [F +]) indicators in the biofilms and in the corresponding wastewaters at 4 and 20 dgrees C. Additionally, we assessed the monthly occurrence of these bacterial and viral indicators as well as of pathogenic protozoa (Cryptosporidium oocysts and Giardia cysts) in three native wastewater biofilms for four months. Our results show that viral indicators (SC and F + ) persist longer in biofilms than in the corresponding wastewaters at 4 degrees C as well as at 20 degrees C. In contrast, persistence of bacterial indicators (TC and HPC) depends on both the temperature and the matrix. Differences between viral and bacterial persistence are discussed. Monthly analysis of native wastewater biofilms shows that bacterial and viral indicators, as well as Cryptosporidium oocysts and Giardia cysts, attach to wastewater biofilms to a concentration that remains stable in time, probably as a result of a dynamic equilibrium between attachment and detachment processes.